U.S. patent number 9,781,736 [Application Number 14/668,644] was granted by the patent office on 2017-10-03 for offloading of controlling across access nodes.
This patent grant is currently assigned to Huawei Technologies Co., Ltd.. The grantee listed for this patent is Huawei Technologies Co., Ltd.. Invention is credited to Aaron Callard, Philippe Leroux, Nimal Gamini Senarath.
United States Patent |
9,781,736 |
Leroux , et al. |
October 3, 2017 |
Offloading of controlling across access nodes
Abstract
Inter-cell interference can be reduced by re-assigning uplink
scheduling responsibilities for a user equipment (UE) from a
controller associated with a serving access point (AP) to a
controller associated with a neighboring AP, as the controller
associated with the neighboring AP may have better access to
channel information corresponding to interference experienced by
the neighboring AP as a result of uplink transmissions from the UE.
After the re-assignment, the controller associated with the
neighboring AP may independently schedule an uplink transmission
parameter (e.g., a transmit power level, a modulation coding scheme
level and/or a precoder) of the UE in a manner that mitigates
inter-cell-interference in the neighboring cell.
Inventors: |
Leroux; Philippe (Ottawa,
CA), Callard; Aaron (Ottawa, CA), Senarath;
Nimal Gamini (Ottawa, CA) |
Applicant: |
Name |
City |
State |
Country |
Type |
Huawei Technologies Co., Ltd. |
Shenzhen |
N/A |
CN |
|
|
Assignee: |
Huawei Technologies Co., Ltd.
(Shenzhen, CN)
|
Family
ID: |
56976792 |
Appl.
No.: |
14/668,644 |
Filed: |
March 25, 2015 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20160286568 A1 |
Sep 29, 2016 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04L
47/60 (20130101); H04L 47/782 (20130101); H04L
5/0032 (20130101); H04L 5/0091 (20130101); H04W
52/146 (20130101); H04L 5/0023 (20130101); H04L
5/0033 (20130101); H04L 1/00 (20130101); H04W
52/243 (20130101); H04W 72/12 (20130101); H04J
11/0056 (20130101); H04L 67/1095 (20130101); H04L
5/0073 (20130101); H04W 72/1231 (20130101); H04W
88/02 (20130101); H04W 28/18 (20130101); H04L
5/0069 (20130101); H04W 88/12 (20130101); H04L
5/0007 (20130101); H04W 88/08 (20130101) |
Current International
Class: |
H04W
72/12 (20090101); H04W 52/24 (20090101); H04W
52/14 (20090101); H04L 29/08 (20060101); H04L
5/00 (20060101); H04L 12/869 (20130101); H04L
12/911 (20130101); H04L 1/00 (20060101); H04W
88/08 (20090101); H04W 88/12 (20090101); H04W
88/02 (20090101); H04W 28/18 (20090101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
Diehm, F., et al., "A Low-Complexity Algorithm for Uplink
Scheduling in Cooperative Cellular Networks with a
Capacity-Constrained Backhaul Infrastructure," Global
Telecommunications Conference, Nov. 30, 2009-Dec. 4, 2009, pp. 1-6,
IEEE. cited by applicant .
Marsch, P., et al., "A Decentralized Optimization Approach to
Backhaul-Constrained Distributed Antenna Systems," Mobile and
Wireless Communications Summit, Jul. 1-5, 2007, pp. 1-5, IEEE.
cited by applicant.
|
Primary Examiner: Mered; Habte
Attorney, Agent or Firm: Slater Matsil, LLP
Claims
What is claimed is:
1. A method for offloading scheduling responsibilities, the method
comprising: identifying, by a second controller associated with a
neighboring access point (AP), a served user equipment (UE)
assigned to a serving AP; obtaining, by the second controller, an
indication that at least a portion of uplink scheduling
responsibilities for the served UE have been re-assigned from a
first controller associated with the serving AP to the second
controller associated with the neighboring AP; and scheduling, by
the second controller, at least one uplink transmission parameter
of an uplink transmission from the served UE to the serving AP
after the portion of uplink scheduling responsibilities are
re-assigned to the second controller, wherein the uplink
transmission parameter is independently scheduled by the second
controller without the first controller participating in scheduling
of the uplink transmission parameter, and wherein the neighboring
AP is incapable of decoding the uplink transmission of the served
UE.
2. The method of claim 1, wherein uplink transmissions from the
served UE to the serving AP interfere with, or are projected to
interfere with, wireless signals communicated by a neighboring
AP.
3. The method of claim 2, wherein scheduling the at least one
uplink transmission parameter of the uplink transmission from the
served UE to the serving AP comprises: scheduling the at least one
uplink transmission parameter of the uplink transmission from the
served UE to the serving AP to mitigate interference experienced by
the neighboring AP as a result of the uplink transmission.
4. The method of claim 1, wherein scheduling the at least one
uplink transmission parameter of the uplink transmission from the
served UE to the serving AP comprises: scheduling the uplink
transmission over different time-frequency resources than uplink
signals received by the neighboring AP.
5. The method of claim 4, wherein scheduling the at least one
uplink transmission parameter of the uplink transmission from the
served UE to the serving AP comprises: scheduling the uplink
transmission over time-frequency resources carrying downlink
signals communicated by the neighboring AP to remotely located UEs,
the remotely located UEs being located at least a threshold
distance from the served UE.
6. The method of claim 1, wherein scheduling the at least one
uplink transmission parameter of the uplink transmission from the
served UE to the serving AP comprises: receiving, by the second
controller, channel information from the neighboring AP, the
channel information corresponding to a signal previously
transmitted by the served UE; and scheduling, by the second
controller, the at least one uplink transmission parameter of the
uplink transmission in accordance with the channel information.
7. The method of claim 6, wherein scheduling the at least one
uplink transmission parameter of the uplink transmission in
accordance with the channel information comprises: assigning a
transmit power level of the uplink transmission in accordance with
the channel information such that a received signal power of the
uplink transmission at the neighboring AP is less than a
threshold.
8. The method of claim 6, wherein scheduling the at least one
uplink transmission parameter of the uplink transmission in
accordance with the channel information comprises: scheduling a
precoder of the uplink transmission in accordance with the channel
information.
9. The method of claim 8, wherein the precoder is configured to
produce destructive interference at a spatial location of the
neighboring AP such that a received signal power of the uplink
transmission at the neighboring AP is less than a threshold.
10. The method of claim 1, wherein uplink transmissions from the
served UE to the serving AP interfere with, or are projected to
interfere with, uplink signals received by the neighboring AP.
11. The method of claim 1, wherein uplink transmissions from the
served UE to the serving AP interfere with, or are projected to
interfere with, downlink signals transmitted by the neighboring
AP.
12. The method of claim 1, further comprising: prompting, by the
second controller, the neighboring AP to signal a scheduling grant
to the served UE, the scheduling grant indicating scheduling
information for the uplink transmission.
13. A second controller associated with a neighboring access point
(AP), the second controller comprising: a processor; and a
non-transitory computer readable storage medium storing programming
for execution by the processor, the programming including
instructions to: identify a served user equipment (UE) assigned to
a serving AP; obtain an indication that at least a portion of
uplink scheduling responsibilities for the served UE have been
re-assigned from a first controller associated with the serving AP
to the second controller associated with the neighboring AP; and
schedule at least one uplink transmission parameter of an uplink
transmission from the served UE to the serving AP after the portion
of uplink scheduling responsibilities are re-assigned to the second
controller, wherein the uplink transmission parameter is
independently scheduled by the second controller without the first
controller participating in scheduling of the uplink transmission
parameter, and wherein the neighboring AP is incapable of decoding
the uplink transmission of the served UE.
14. The second controller of claim 13, wherein the instructions to
schedule the at least one uplink transmission parameter of an
uplink transmission from the served UE to the serving AP include
instructions to: schedule the uplink transmission over different
time-frequency resources than uplink signals received by the
neighboring AP.
15. The second controller of claim 13, wherein the instructions to
schedule the at least one uplink transmission parameter of an
uplink transmission from the served UE to the serving AP include
instructions to: receive channel information from the neighboring
AP, the channel information corresponding to a signal previously
transmitted by the served UE; and schedule the at least one uplink
transmission parameter of the uplink transmission in accordance
with the channel information, wherein the at least one uplink
transmission parameter comprises at least one of a transmit power
level and a precoder.
16. The second controller of claim 15, wherein the instructions to
scheduling the at least one uplink transmission parameter of the
uplink transmission in accordance with the channel information
includes instructions to: assign a transmit power level of the
uplink transmission in accordance with the channel information such
that a received signal power of the uplink transmission at the
neighboring AP is less than a threshold.
17. A method for uplink communications, the method comprising:
receiving, by a served user equipment (UE), a first scheduling
assignment from a first controller; performing, by the served UE, a
first uplink transmission over a radio interface between the served
UE and a serving access point (AP) in accordance with the first
scheduling assignment during a first period, the first controller
being associated with the serving AP; receiving, by the served UE,
at least one uplink transmission parameter from a second
controller, the second controller being associated with a
neighboring AP, wherein the at least one uplink transmission
parameter is independently scheduled by the second controller
without the first controller participating in scheduling of the at
least one uplink transmission parameter; and performing, by the UE,
a second uplink transmission over the radio interface in accordance
with the at least one uplink transmission parameter during a second
period, the second uplink transmission being received at least by
the serving AP, wherein the neighboring AP is incapable of decoding
uplink transmissions of the served UE.
18. A served user equipment (UE) comprising: a processor; and a
non-transitory computer readable storage medium storing programming
for execution by the processor, the programming including
instructions to: receive a first scheduling assignment from a first
controller; perform a first uplink transmission to over a radio
interface between the served UE and a serving access point (AP) in
accordance with the first scheduling assignment during a first
period, the first controller being associated with the serving AP;
receive at least one uplink transmission parameter from a second
controller, the second controller being associated with a
neighboring AP, wherein the at least one uplink transmission
parameter is independently scheduled by the second controller
without the first controller participating in scheduling of the at
least one uplink transmission parameter; and perform a second
uplink transmission over the radio interface in accordance with the
at least one uplink transmission parameter during a second period,
the second uplink transmission being received at least by the
serving AP, wherein the neighboring AP is incapable of decoding
uplink transmissions of the served UE.
19. The served UE of claim 18, wherein the at least one uplink
transmission parameter specifies an uplink resource for carrying
the second uplink transmission.
20. The served UE of claim 18, wherein the at least one uplink
transmission parameter specifies a transmit power level for the
second uplink transmission.
21. The served UE of claim 18, wherein the at least one uplink
transmission parameter specifies a precoder for the second uplink
transmission.
22. The method of claim 17, wherein the at least one uplink
transmission parameter specifies a transmit power level for the
second uplink transmission.
Description
TECHNICAL FIELD
The present invention relates to the field of wireless
communications, and, in particular embodiments, to a system and
method for offloading of controlling across access nodes.
BACKGROUND
Traditionally, radio access links between access points (APs) and
user equipment (UEs) have been the bottleneck that constrains
throughput between the UE and the core network, as data rates over
backhaul network connection between the radio access network (RAN)
and the core network are typically many times faster than data
rates over the corresponding wireless access links. However,
next-generation network architectures having densely deployed cells
may achieve significant increases in throughput, as well as share
backhaul network resources amongst greater numbers of APs. As a
result, the capacity gap between radio access links and backhaul
network connection may be reduced in some network-generation
network implementations, resulting in situations where data
forwarding rates are constrained by the backhaul network
connection, rather than the radio access link.
SUMMARY OF THE INVENTION
Technical advantages are generally achieved, by embodiments of this
disclosure which describe offloading of controlling across access
node.
In accordance with an embodiment, a method for offloading
scheduling responsibilities is provided. In this example, the
method comprises identifying a served user equipment (UE) assigned
to a serving AP. Uplink transmissions from the served UE to the
serving AP interfere with, or are projected to interfere with,
wireless signals communicated by a neighboring AP. The method
further comprises determining that at least a portion of uplink
scheduling responsibilities for the served UE have been re-assigned
from a first controller associated with the serving AP to a second
controller associated with the neighboring AP. The method further
comprises scheduling a parameter of an uplink transmission from the
served UE to the serving AP to mitigate interference experienced by
the neighboring AP as a result of the uplink transmission. The
parameter of the uplink transmission is independently scheduled by
the second controller without the first controller participating in
scheduling of the parameter. An apparatus for performing this
method is also provided.
In accordance with another embodiment, a method for uplink
communications is provided. In this example, the method comprises
receiving a first scheduling assignment from a first controller,
performing a first uplink transmission to the serving AP over the
radio interface in accordance with the first scheduling assignment
during a first period, and receiving a second scheduling assignment
from a second controller. The second scheduling assignment
indicates a parameter that is independently scheduled by the second
controller without the first controller participating in scheduling
of the parameter. The method further comprises performing a second
uplink transmission over the radio interface in accordance with the
parameter during a second period. The second uplink transmission is
received at least by the serving AP. An apparatus for performing
this method is also provided.
BRIEF DESCRIPTION OF THE DRAWINGS
For a more complete understanding of the present disclosure, and
the advantages thereof, reference is now made to the following
descriptions taken in conjunction with the accompanying drawings,
in which:
FIG. 1 illustrates a diagram of an embodiment wireless network;
FIG. 2 illustrates a diagram of an embodiment network architecture
for an offloading control method;
FIG. 3 illustrates a flow chart of an embodiment method for
offloading scheduling responsibilities;
FIG. 4 illustrates a flow chart of an embodiment method for
re-assigning scheduling responsibilities;
FIG. 5 illustrates a flow chart of an embodiment method for
performing uplink transmissions after the re-assignment of
scheduling responsibilities;
FIG. 6 illustrates a diagram of an embodiment co-coordination
function;
FIG. 7 illustrates a diagram of an embodiment communications
device; and
FIG. 8 illustrates a diagram of an embodiment computing
platform.
Corresponding numerals and symbols in the different figures
generally refer to corresponding parts unless otherwise indicated.
The figures are drawn to clearly illustrate the relevant aspects of
the embodiments and are not necessarily drawn to scale.
DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
The making and using of embodiments of this disclosure are
discussed in detail below. It should be appreciated, however, that
the concepts disclosed herein can be embodied in a wide variety of
specific contexts, and that the specific embodiments discussed
herein are merely illustrative and do not serve to limit the scope
of the claims. Further, it should be understood that various
changes, substitutions and alterations can be made herein without
departing from the spirit and scope of this disclosure as defined
by the appended claims.
In densely deployed wireless networks, uplink scheduling may
attempt to maximize the data rate of uplink transmissions in a
serving cell, while mitigating inter-cell interference in
neighboring cells. This may be complicated in distributed
scheduling scenarios, where different controllers schedule
transmissions in different cells. For example, a distributed
controller allocating transmissions in a serving cell may have
limited access to control information (e.g., channel state
information (CSI)) corresponding to a neighboring cell, and
consequently may find it difficult to determine which transmission
parameters would provide acceptable interference levels in the
neighboring cell.
Aspects of this disclosure re-assign uplink scheduling
responsibilities for a served UE from a controller associated with
a serving cell to a controller associated with a neighboring cell
such that the controller associated with the neighboring cell
independently schedules an uplink transmission parameter (e.g., a
transmit power level, a modulation coding scheme (MCS) level,
and/or a precoder) to the served UE. This re-assignment may be
advantageous because the controller associated with the neighboring
cell may have better access to CSI measured in the neighboring
cell, and may therefore be better situated to schedule uplink
transmission parameters of the served UE that mitigate
inter-cell-interference in the neighboring cell. In one example,
the controller associated with the neighboring cell may schedule
the uplink transmission of the served UE over radio resources are
not being utilized by the neighboring AP, or are otherwise carrying
signals that would experience less interference from the uplink
transmission, e.g., downlink signals transmitted to UEs in the
neighboring cell that are positioned far away from the served UE,
etc. As another example, the neighboring controller may schedule
the transmission parameters in a manner that allows the neighboring
AP to decode, and isolate, the uplink transmission from other
received signals in accordance with an interference cancellation
technique, e.g., successive interference cancellation (SIC), etc.
These and other aspects are discussed in greater detail below.
Aspects of this disclosure may be implemented in wireless networks.
FIG. 1 illustrates a network 100 for communicating data. The
network 100 comprises an access point (AP) 110 having a coverage
area 101, a plurality of mobile devices 120, and a backhaul network
130. The AP 110 may comprise any component capable of providing
wireless access by, inter alia, establishing uplink (dashed line)
and/or downlink (dotted line) connections with the mobile devices
120, such as a base station, an enhanced base station (eNB), a
femtocell, and other wirelessly enabled devices. The mobile devices
120 may comprise any component capable of establishing a wireless
connection with the AP 110, such as user equipment (UE), a mobile
station (STA), or other wirelessly enabled devices. The backhaul
network 130 may be any component or collection of components that
allow data to be exchanged between the AP 110 and a remote end (not
shown). In some embodiments, the network 100 may comprise various
other wireless devices, such as relays, low power nodes, etc.
FIG. 2 illustrates an embodiment network architecture 200 for
re-assigning scheduling responsibilities. As shown, the network
architecture 200 comprises a gateway 205, controllers 215, 225,
access points (APs) 210, 220, and user equipments (UEs) 230, 240.
The gateway 205 communicates with the APs 210, 220 through the
backhaul network connections 201, 202, respectively. In this
example, the UE 230 may be served by the AP 210, and consequently
the UE 230 and the AP 210 may be referred to as the served UE 230
and the serving AP 210, respectively. For similar reasons, the AP
220 may be referred to as the neighboring AP 220.
The served UE 230 may perform uplink transmissions to the serving
AP 210 over the radio interface 231. Those uplink transmissions may
also propagate over a radio interface 232, and ultimately produce
interference at the neighboring AP 220. For example, uplink
transmissions by the served UE 230 may interfere with uplink
transmissions communicated from the UE 240 to the neighboring AP
220 over the radio interface 221.
The controller 215 may be associated with the AP 210, such that the
controller 215 generally performs uplink scheduling for the serving
AP 210. Likewise, the controller 225 may be associated with the
neighboring AP 220 to the extent that the controller 215 generally
performs uplink scheduling for the neighboring AP 220. The
controllers 215, 225 may be deployed on the same device platform or
on different device platforms, as the respective APs 210, 220.
In some situations, it may be advantageous to re-assign at least a
portion of uplink scheduling responsibility of the served UE 230
from the controller 215 to the controller 225. The phrase
"re-assignment of scheduling responsibilities" for the served UE
230 from the controller 215 associated with the serving AP 210 to
the controller 225 associated with the neighboring AP 220 is used
loosely herein to indicate that at least a portion of scheduling
responsibilities for the served UE 230 have been assigned to the
controller 225. Therefore, unless otherwise specified, the phrase
"re-assignment of scheduling responsibilities" for the served UE
230 from the controller 215 associated with the serving AP 210 to
the controller 225 associated with the neighboring AP 220 does not
imply that the controller 215 associated with the serving AP 210
previously scheduled an uplink transmission of the served UE 230.
For example, in some embodiments, the aforementioned "re-assignment
of scheduling responsibility" occurs prior to the served UE 230
ever performing an uplink transmission to the served AP 220. In
such an example, the re-assignment may occur during
link-setup/discovery upon determining that that uplink
transmissions from the served UE 230 to the serving AP are
projected to interfere with signals communicated by the neighboring
AP 220. The projection may be based on a non-scheduled transmission
(e.g., link-setup/discovery message) of the served UE 230. In other
embodiments, the re-assignment of scheduling responsibility occurs
between uplink transmissions of the served UE 230. For example, the
served UE 230 may perform a first uplink transmission to the
serving AP 210 that is scheduled by the controller 215. The first
uplink transmission may produce a threshold level of interference
at the neighboring AP 220, which may trigger the re-assignment of
scheduling responsibilities for the served UE 230 from the
controller 215 to the controller 225.
The re-assignment of scheduling responsibilities may be triggered
by different network devices. For example, one of the controllers
215, 225 may request that scheduling responsibilities for the
served UE 230 be transferred to the controller 225. The request may
be exchanged between the controllers 215, 225, or between one of
the controllers 215, 225 and a third party component, e.g., a
co-coordination function or central entity responsible for
assigning/re-assigning scheduling responsibilities between
controllers. The request may include various information, including
the reason for requesting the re-assignment of scheduling
responsibilities. In other embodiments, the re-assignment is
triggered unilaterally by a third party component, e.g., a
co-coordination function or central entity responsible for
assigning/re-assigning scheduling responsibilities between
controllers.
The re-assignment of scheduling may be triggered by exchanging
control signaling (e.g., requests, instructions, etc.) between the
controllers 215, 225 and/or a central controller. For example, the
controller 215 may send a re-assignment request/indication to the
controller 225, or vice-versa, to trigger the re-assignment of
scheduling responsibilities. Alternatively, a central controller
may communicate a re-assignment instructions to one or both of the
controllers 215, 225 to trigger the re-assignment of scheduling
responsibilities. As discussed above, the re-assignment of uplink
scheduling responsibility may be triggered when an uplink
transmission of the served UE 230 interferes with, or is projected
to interfere with, wireless signals communicated by the neighboring
AP 220, e.g., the measured or projected level of
inter-cell-interference exceeds a threshold. Other criteria may
also trigger the transfer of scheduling responsibility, such as the
amount of available bandwidth over the backhaul network connections
201, 202, loading of the APs 210, 220, available resources of the
APs 210, 220, spectral efficiency of the wireless network, etc. For
example, if the bandwidth on the backhaul connection 201 is
constrained, then it may be unable to support high data rates over
the serving link 231. In such cases, a network device (e.g., the
controller 215, a central controller, etc.) may trigger at least
some scheduling responsibilities to be re-assigned to the
controller 225 in order to reduce inter-cell-interference. As
another example, if there is a disparity in available resources at
the APs 210, 220 (e.g., the AP 220 has fewer available resources
that need to managed efficiently), then a network device (e.g., the
controller 225, a central controller, etc.) may trigger the
reassignment of at least some scheduling responsibilities to the
controller 225. This may allow the controller 225 to select
resources (and/or other parameters) over which to communicate an
uplink transmission from the UE 230 to the AP 210 in a manner that
mitigates interference over the limited available resources of the
AP 220. As yet another example, a network device (e.g., a central
controller, etc.) may trigger the reassignment of at least some
scheduling responsibilities to the controller 225 when reducing
inter-cell-interference in the neighboring cell will improve the
spectral efficiency of the wireless network, e.g., even at the
expense of reduced throughput over access link 231. In some
embodiments, a cost function is used to determine when to re-assign
uplink scheduling responsibilities. The cost function may include
various components, including an interference component, a spectral
efficiency component, and an available bandwidth component. The
spectral efficiency component may correspond to a spectral
efficiency over a wireless network that includes both the serving
cell and base cell. The available bandwidth component may
correspond to the amount of bandwidth available to the respective
APs. The cost function may trigger the re-assignment of scheduling
responsibilities when a cost value exceeds a threshold. In some
embodiments, the cost function may include hysteresis parameters to
prevent scheduling responsibilities form being re-assigned too
frequently. The cost function may also include parameters related
to the loading of APs relative to available resources (e.g.,
bandwidth availabilities, backhaul resource availability,
processing capacities) and/or AP capabilities (e.g., MIMO
capabilities, processing capabilities, etc.).
After being re-assigned scheduling responsibilities of the served
UE 230, the controller 225 may independently assign one or more
uplink scheduling parameters (e.g., an MCS level, a transmit power
level, a precoder, etc.) to the served UE 230. The uplink
scheduling paramaters may be communicated through a control channel
(e.g., a physical downlink control channel (PDCCH) or some other
type of signaling, e.g., higher layer signaling, etc. The assigned
uplink scheduling parameters may be used by the served UE 230 when
performing uplink transmissions to the serving AP 210 over the
radio interface 231. In an embodiment, one or more of a transmit
power level, precoder, MCS level, and resource assignment may be
communicated from the controller 225 to the served UE 230 to
mitigate interference experienced by the AP 220 as a result of
those uplink transmissions.
In some embodiments, the controller 225 schedules the uplink
transmission of the served UE 230 in a manner that avoids
interfering with signals communicated by the AP 220. For example,
the controller 225 may schedule the uplink transmission over
resources that are not being used by the AP 220. As another
example, the controller 225 may schedule the uplink transmission
over resources that are carrying downlink transmissions to a UE
that is positioned relatively far from the served UE 230, e.g., a
UE on the other-side of the neighboring cell, etc. As yet another
example, the controller 225 may reduce a transmit power of the
uplink transmission of the served UE 230, or assign a precoder that
directs a beam of the uplink transmissions of the served UE 230
away from a spatial location of the AP 220.
In other embodiments, the controller 225 may schedule the uplink
transmission of the served UE 230 in a manner that allows the AP
220 to isolate interference resulting from those uplink
transmissions from received signals (e.g., an uplink transmission
from the UE 240) using an interference cancellation technique,
e.g., SIC, etc. For example, the controller 225 may assign uplink
transmission parameters (e.g., MCS level, transmit power level,
precoder etc.) to the served UE 230 that allow the AP 220 to decode
the resulting uplink transmission of the served UE 230. The AP 220
may then isolate the decoded uplink transmission of the served UE
230 from a received signal (e.g., an uplink transmission from the
UE 240) using an interference cancellation technique. To increase
the probability that the uplink transmission propagating over the
radio interface 232 will be correctly decoded at the AP 220, the
controller 225 may reduce the MCS level, increase the transmit
power, and/or assign an uplink precoder that creates constructive
interference at the spatial location of the AP 220.
In yet other embodiments, the controller 225 may schedule the
uplink transmission of the served UE 230 in accordance with a
multi-point reception scheme. In such embodiments, the uplink
transmission may be jointly received and decoded by the APs, 210,
220. The resulting decoded signals may then be forwarded over the
backhaul network connections 201, 202 to the gateway 205, where the
decoded signals may be combined.
FIG. 3 illustrates a flow chart of an embodiment method 300 for
offloading scheduling responsibilities, as may be performed by a
controller associated with a neighboring AP. As shown, the method
300 begins at step 310, where the controller identifies a served UE
assigned to a serving AP. Subsequently, the method 300 proceeds to
step 320, where the second controller determines that at least a
portion of uplink scheduling responsibilities for the served UE
have been re-assigned from a controller associated with the serving
AP to a controller associated with the neighboring AP. Finally, the
method 300 proceeds to step 330, where the controller associated
with the neighboring AP schedules a parameter of an uplink
transmission from the served UE to the serving AP. The controller
may schedule the parameter using channel information received from
the neighboring AP and/or other information (e.g., buffer sizes, AP
loading, QoS demands, etc.) to mitigate interference experienced by
the neighboring AP as a result of the uplink transmission. The
channel information may indicate a characteristic (e.g., path loss,
received signal power, etc.) obtained from a previous transmission
of the served UE that was received by the neighboring AP, e.g.,
uplink transmission, sounding signal transmission, etc. In some
embodiments, the controller uses the channel information to assign
an uplink transmission parameter to the served UE that reduces a
received signal power of the resulting uplink transmission at the
neighboring AP below a threshold, e.g., a 3db threshold or
otherwise. For example, the controller may assign a transmit power
level that is below a threshold to reduce the received signal power
at the neighboring AP. As another example, the controller may
assign a precoder that produces destructive interference at a
spatial location of the neighboring AP. In other embodiments, the
controller uses the channel information to assign an uplink
transmission parameter to the served UE that produces a successful
decoding probability of the resulting uplink transmission at the
neighboring AP exceeds a threshold, e.g., ninety percent, etc. For
example, the controller may assign a transmit power level that is
above a threshold to increase the received signal power at the
neighboring AP. As another example, the controller may assign a
precoder that produces constructive interference at a spatial
location of the neighboring AP. As yet another example, the
controller may assign an MCS level that is below a threshold to
reduce the complexity of decoding, e.g., to reduce the level of
reception quality needed to properly decode the signal. This may
allow the neighboring AP to isolate the uplink transmission from
received signals in accordance with an interference cancellation
technique, thereby mitigating interference.
FIG. 4 illustrates a flow chart of an embodiment method 400 for
re-assigning scheduling responsibilities, as may be performed by a
network device, e.g., a controller, a gateway, an independent
scheduling re-assignment agent, etc. As shown, the method 400
begins at step 410, where the network device identifies a served UE
that is assigned to a serving AP. Subsequently, the method 400
proceeds to step 420, where the network device determines that
uplink transmissions communicated from the served UE to the serving
AP interfere with, or are projected to interfere with, wireless
transmissions communicated by a neighboring AP. Finally, the method
400 proceeds to step 430, where the network device re-assigns at
least a portion of uplink scheduling responsibilities for the
served UE from a controller associated with the serving AP to a
controller associated with the neighboring AP.
FIG. 5 illustrates a flow chart of an embodiment method 500 for
performing uplink transmissions after the re-assignment of
scheduling responsibilities, as might be performed by a served UE.
As shown, the method 500 begins at step 510, where the served UE
establishes a radio interface with a serving AP. Next, the method
500 proceeds to step 520, where the served UE receives a first
scheduling assignment from a controller associated with the serving
AP. Subsequently, the method 500 proceeds to step 530, where the
served UE performs uplink transmissions to the serving AP over the
radio interface in accordance with the first scheduling assignment.
Thereafter, the method 500 proceeds to step 540, where the served
UE receives a second scheduling assignment from a controller
associated with a neighboring AP. Finally, the method 500 proceeds
to step 550, where the served UE performs uplink transmissions to
the serving AP over the radio interface in accordance with the
second scheduling assignment.
FIG. 6 illustrates a diagram of an embodiment co-coordination
function 600. As shown, the embodiment co-coordination function 600
considers backhaul parameters, access link parameters, and UE
quality of service requirements when determining whether to
re-assign scheduling responsibilities. In an embodiment, the
co-ordination function 600 identifies UEs that produce the most
interference, and arranges them into groups. The co-ordination
function may then assign controllers to the groups of UEs, and
determine which information the APs must push to which controllers.
The information may include channel state information (CSI), mean
spectral efficiency (SE) information, maximum MCS levels, resource
block masks, long term signal-to-noise (SNR) ratios between the UE
and an AP, precoders, power parameters, power masks, and resource
restrictions (e.g., resource block (RB) restrictions), etc.
Resource restrictions may include a defined set or range of
resources to be used for reducing inter-cell interference
coordination (ICIC) purposes. The information may also include a
time stamp so that the receiving controller can understand how old
the information is. If the information is deemed outdated, then the
device may take steps to obtain more accurate/up-to-date
information, e.g., requesting updated information, performing
channel estimation, etc. The information can be sent in a handover,
or when a receiver detects a triggering event (e.g., a change in
link quality, a spike in interference, etc.), or when a mobility
predictor determines that it is time for an update.
In some embodiments, the assignment/re-assignment of scheduling
responsibilities may be performed by a co-coordination entity. The
co-coordination entity may be located at a controller, an access
point, or some third party device, e.g., a central controller. The
co-coordination function may consider various criteria when
determining whether to transfer scheduling responsibility from one
controller to another.
The co-coordination function 600 may then notify network devices
(e.g., controllers, APs, etc.) of the serving AP assignments, the
controller assignments, access point directives, and controller
directives. The access point directives may notify the AP of which
information needs to be provided to which APs. The controller
directives may indicate scheduling policies to be used for certain
UEs and/or groups of UEs. The co-coordination function 600 may
re-assign scheduling responsibilities in a variety of ways. In one
example, the co-coordination function 600 notifies one or more of
the controllers that the scheduling responsibilities have been
re-assigned.
FIG. 7 illustrates a block diagram of an embodiment communications
device 700, which may be equivalent to one or more devices (e.g.,
requesting devices, candidate devices, network nodes, etc.)
discussed above. The communications device 700 may include a
processor 704, a memory 706, and a plurality of interfaces 710,
712, 714, which may (or may not) be arranged as shown in FIG. 7.
The processor 704 may be any component capable of performing
computations and/or other processing related tasks, and the memory
706 may be any component capable of storing programming and/or
instructions for the processor 704. The interfaces 710, 712, 714
may be any component or collection of components that allows the
communications device 700 to communicate with other devices, and
may include wireless interfaces and/or wireline interfaces for
communicating over radio interfaces, backhaul interfaces, control
channels, etc.
FIG. 8 is a block diagram of a processing system that may be used
for implementing the devices and methods disclosed herein. Specific
devices may utilize all of the components shown, or only a subset
of the components, and levels of integration may vary from device
to device. Furthermore, a device may contain multiple instances of
a component, such as multiple processing units, processors,
memories, transmitters, receivers, etc. The processing system may
comprise a processing unit equipped with one or more input/output
devices, such as a speaker, microphone, mouse, touchscreen, keypad,
keyboard, printer, display, and the like. The processing unit may
include a central processing unit (CPU), memory, a mass storage
device, a video adapter, and an I/O interface connected to a
bus.
The bus may be one or more of any type of several bus architectures
including a memory bus or memory controller, a peripheral bus,
video bus, or the like. The CPU may comprise any type of electronic
data processor. The memory may comprise any type of non-transitory
system memory such as static random access memory (SRAM), dynamic
random access memory (DRAM), synchronous DRAM (SDRAM), read-only
memory (ROM), a combination thereof, or the like. In an embodiment,
the memory may include ROM for use at boot-up, and DRAM for program
and data storage for use while executing programs.
The mass storage device may comprise any type of non-transitory
storage device configured to store data, programs, and other
information and to make the data, programs, and other information
accessible via the bus. The mass storage device may comprise, for
example, one or more of a solid state drive, hard disk drive, a
magnetic disk drive, an optical disk drive, or the like.
The video adapter and the I/O interface provide interfaces to
couple external input and output devices to the processing unit. As
illustrated, examples of input and output devices include the
display coupled to the video adapter and the mouse/keyboard/printer
coupled to the I/O interface. Other devices may be coupled to the
processing unit, and additional or fewer interface cards may be
utilized. For example, a serial interface such as Universal Serial
Bus (USB) (not shown) may be used to provide an interface for a
printer.
The processing unit also includes one or more network interfaces,
which may comprise wired links, such as an Ethernet cable or the
like, and/or wireless links to access nodes or different networks.
The network interface allows the processing unit to communicate
with remote units via the networks. For example, the network
interface may provide wireless communication via one or more
transmitters/transmit antennas and one or more receivers/receive
antennas. In an embodiment, the processing unit is coupled to a
local-area network or a wide-area network for data processing and
communications with remote devices, such as other processing units,
the Internet, remote storage facilities, or the like.
While this invention has been described with reference to
illustrative embodiments, this description is not intended to be
construed in a limiting sense. Various modifications and
combinations of the illustrative embodiments, as well as other
embodiments of the invention, will be apparent to persons skilled
in the art upon reference to the description. It is therefore
intended that the appended claims encompass any such modifications
or embodiments.
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